[Java] 백준 2252 쉬운 위상정렬

https://www.acmicpc.net/problem/2252

배열에 컬렉션프레임웍을 선언해 놓은 뒤 후위 노드들을 add해 주었다.

위상정렬 개념을 익히기에 좋은 문제다.

import java.util.LinkedList;
import java.util.Scanner;
public class Problem2252_TopologicalSort2 {
	
	public static void main(String[] args) {
		
		Scanner sc = new Scanner(System.in);
		
		int n = sc.nextInt();
		int m = sc.nextInt();
		
		LinkedList<Integer> graph[] = new LinkedList[n+1];
		int indegree[] = new int[n+1];
		
		for(int i=1; i<n+1; i++){
			graph[i] = new LinkedList<>();
		}
		
		int from, to;
		for(int i=0; i<m; i++){
			from = sc.nextInt();
			to = sc.nextInt();
			
			graph[from].add(to);
			indegree[to]++;
		}
		
		LinkedList<Integer> q = new LinkedList<>();
		
		for(int i=1; i<n+1; i++){
			if(indegree[i]==0){
				q.offer(i);
				System.out.print(i+" ");
			}
		}
		
		while(!q.isEmpty()){
			int zeroNode = q.poll();
			for (int node : graph[zeroNode]) {
				indegree[node]--;
				if(indegree[node]==0){
					q.add(node);
					System.out.print(node+" ");
				}
			}
			
		}
		
	}
}